Re: [PATCH v4 6/6] tests/qtest: migration-test: Add tests for file-based migration

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Jul 11, 2023 at 07:27:42PM -0300, Fabiano Rosas wrote:
> Fabiano Rosas <farosas@suse.de> writes:
> 
> > Add basic tests for file-based migration.
> >
> > Signed-off-by: Fabiano Rosas <farosas@suse.de>
> > Reviewed-by: Peter Xu <peterx@redhat.com>
> > ---
> >  tests/qtest/migration-test.c | 99 ++++++++++++++++++++++++++++++++++++
> >  1 file changed, 99 insertions(+)
> >
> > diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
> > index 2fdf6a115e..c052dbe1f1 100644
> > --- a/tests/qtest/migration-test.c
> > +++ b/tests/qtest/migration-test.c
> > @@ -52,6 +52,10 @@ static bool got_dst_resume;
> >   */
> >  #define DIRTYLIMIT_TOLERANCE_RANGE  25  /* MB/s */
> >  
> > +#define QEMU_VM_FILE_MAGIC 0x5145564d
> > +#define FILE_TEST_FILENAME "migfile"
> > +#define FILE_TEST_OFFSET 0x1000
> > +
> >  #if defined(__linux__)
> >  #include <sys/syscall.h>
> >  #include <sys/vfs.h>
> > @@ -762,6 +766,7 @@ static void test_migrate_end(QTestState *from, QTestState *to, bool test_dest)
> >      cleanup("migsocket");
> >      cleanup("src_serial");
> >      cleanup("dest_serial");
> > +    cleanup(FILE_TEST_FILENAME);
> >  }
> >  
> >  #ifdef CONFIG_GNUTLS
> > @@ -1459,11 +1464,28 @@ static void test_precopy_common(MigrateCommon *args)
> >               */
> >              wait_for_migration_complete(from);
> >  
> > +            /*
> > +             * For file based migration the target must begin its
> > +             * migration after the source has finished.
> > +             */
> > +            if (strstr(connect_uri, "file:")) {
> > +                migrate_incoming_qmp(to, connect_uri, "{}");
> > +            }
> > +
> 
> This is now broken since we merged commit e02f56e3de ("tests/qtest:
> massively speed up migration-test").
> 
> We cannot monitor the destination while the source is still running
> because we need the source to have finished writing to the file before
> we can start the destination. I'll have to think of another way of
> testing a migration that is done with a live source but asynchronous
> incoming migration.
> 
> Any suggestions are welcome.

Don't use test_precopy_common() at all. This helper is written from the
POV that we're actually doing a live migration. Migrate to/from file is
not live migration.

So open code the subset of pieces of test_precopy_common() that you
need for file migration. There are a handful of other tests that
take this approach since test_precopy_common wasn't suitable for
them eg test_migrate_auto_converge()

With regards,
Daniel
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